CHAP, xvn.l MAMMALIA. 253 



The Wombats are tail-less, terrestrial, burrowing animals, about 

 the size of a badger, but feeding on roots and grass. They 

 inhabit South Australia and Tasmania (Plate XI. vol. i. p. 439). 



An extinct wombat, as large as a tapir, has been found in the 

 Australian Pliocene deposits. 



General Remarks on the Distribution of Marsupialia. 



We have here the most remarkable case, of an extensive and 

 highly varied order being confined to one very limited area on 

 the earth's surface, the only exception being the opossums in 

 America. It has been already shown that these are compara- 

 tively recent immigrants, which have survived in that country 

 long after they disappeared in Europe. As, however, no other 

 form but that of the Didelphyidse occurs there during the 

 Tertiary period, we must suppose that it was at a far more 

 remote epoch that the ancestral forms of all the other Marsupials 

 entered Australia ; and the curious little mammals of the Oolite 

 and Trias, offer valuable indications as to the time when this 

 really took place. 



A notice of these extinct marsupials of the secondary period 

 will be found at vol. i. p. 159. 



Order XIILMONOTEEMATA. 



FAMILY 83. ORNITHOBHYNCHIDJE. (1 Genus, 1 Species.) 

 GENERAL DISTRIBUTION. 



NEOTROPICAL I NEARCTIC I PAL^EARCTIC 



SUB-REGIONS. SUB-BEGIONS. SUB-REGIONS. 



ETHIOPIAN I ORIENTAL I AUSTRALIAN 

 SUB-REGIONS. SOB-REGIONS. SUB-REGIONS. 



The Ornithorhynchus, or duck-billed Platypus, one of the most 

 remarkable and isolated of existing mammalia, is found in East 

 and South Australia, and Tasmania. 



